I start with a circle for the edge, then model a cross in the middle for the slots, then connect the two pieces, the result is basically the same thing as Lux's in terms of topology, but I use a few more support edges. Start with the cross by itself tho, allows me to set the proportions how I like them. Additionally, I model it flat, then use a proportional move tool with fall off to get the curve.

Core i7 950@3.02GHz | 12GB Corsair Dominator Ram@1600mHz | 2GB Geforce GTX 660

Lightwave | Blender | Marmoset | GIMP | Krita